Despite impressive progress to expand access to HIV testing in antenatal care (ANC) and antiretroviral (ARV) prophylaxis to HIV+ pregnant women, Kenya continues to struggle to provide comprehensive HIV prevention and treatment services for women and infants. Innovative interventions that integrate HIV services and target both system and individual level barriers will maximize the impact of existing efforts to eliminate MTCT of HIV globally. Prospective follow-up and support for mother-infant pairs from prevention of mother-to-child transmission (PMTCT) through early infant diagnosis (EID) services can reduce HIV transmission and maximize the quality of maternal and pediatric care. The HIV Infant Tracking System (HITSystem) is a web-based mHealth, system-level intervention designed and evaluated by our research team that has dramatically improved early infant diagnosis (EID) outcomes by providing efficient prospective tracking of HIV-exposed infants, automated electronic action 'alerts' for both providers and lab technicians to prompt 8 time-sensitive EID interventions, and SMS text messages to mothers when return hospital visits are required. Based on the promising impact of the HITSystem in Kenya, we propose to adapt the design and scope of the HITSystem to target PMTCT for HIV+ pregnant women. Our objective in this application is to modify the HITSystem to engage and retain HIV+ pregnant women throughout antenatal, obstetric, and postnatal services and evaluate its impact on PMTCT related behaviors. The research will be conducted in 3 phases. In Phase 1 we will conduct qualitative research with HIV+ pregnant and postpartum women to tailor text message content and timing, and with healthcare providers engaged in PMTCT care to inform the implementation strategy for Phase 3. In Phase 2, we will adapt the programming of algorithm-driven electronic alerts and patient follow-up features to support PMTCT and identify high-risk mothers for additional support. In Phase 3, we will evaluate the HITSystem 2.0 by randomly assigning HITSystem implementation to one of two closely matched government hospitals. The primary outcome is complete PMTCT retention across three phases of care (before, during and after delivery). Secondary outcomes include ART adherence and infant HIV status.